O.S. .46 AX - bad rear bearing - metal shards... (replaced and running)
 

Spinning my prop by hand didn't feel so right a few weeks ago so I ordered a replacement set of SS bearings. Procrastinated one trip to the field to many to replace them. Had a few high speed legs today that really rev'd my engine and think this did it in as it ran very rough after this. Got home and cracked open the engine...

Metal shards embedded in the head and stuck in the glow plug...
http://somegeek.home.comcast.net/som..._bearing_2.jpg

http://somegeek.home.comcast.net/som..._bearing_3.jpg

Metal shards embedded in the piston...
http://somegeek.home.comcast.net/som..._bearing_5.jpg

Metal shards removed...
http://somegeek.home.comcast.net/som..._bearing_4.jpg

Crankcase damage from chunks being ground between the rod end and the crankcase...
http://somegeek.home.comcast.net/som..._bearing_6.jpg

Rusty rear bearing... * /me gives said rusty bearing the evil eye *
http://somegeek.home.comcast.net/som..._bearing_9.jpg

Rod end damage...
http://somegeek.home.comcast.net/som..._bearing_7.jpg

http://somegeek.home.comcast.net/som...bearing_10.jpg

Surprisingly, there is little if any damage to the piston and sleeve. How those shards migrated up to the head with doing minimal damage is beyond me. I am thinking I could just clean up the crankcase with my dremel, tap down any of the pointy parts of the damage on the rod end(don't really want to remove any material), lap the piston top and put in my new bearing set with a slight loss in compression.

Engine has been run with Cool Power 15% since day one with minimal use of after run oil... thinking I'll at least use a tsp of ATF after a day's flying now.

The rear bearing is the bad part... After removing it, it has a lot of play in it... probably due to rust and then the material that was ejected from it and into the crankcase.

This video on How to change model airplane engine bearings was of great help since I'd never done this before. Heating the crankcase with a heat gun on high was the ticket to remove the bearings.

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Hey, ....at least there is no castor varnish to clean up[:'(] Metal chunks and rust.................

Im thinking the same as you, clean it up, swap out the bearing and run it. If it has compression, it should run.

Those pictures are pretty brutal however[:@]

Do you think that the fuel had anything to do with this bearing failure?

Richard

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Second look at those pics[:@]

That con rod is wasted.........maybe living on browwed time............[:@]

Might want to very carefully remove the gouges and feather them out, also maybe bead blast, sand blast the rod for some stress relief.........
Its probably going to need it.

Let us know how it runs after

Richard

edit spelng[:@]

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Somegeek That is sooo bad!! The gouges in the crankcase are deep. Must be what we heard right before the old dead stick!! It did sound cool though when the bearings were going out!! I think I'd save my expensive rebuild kit for a more worthy motor and replace that one. Anyway, good job landing that plane in the wind today. Tough to get back in against that wind when your engine just took a dump!!

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I learned a long time ago that it's *never* a good idea to try and get "just one more flight" from an engine once you notice that the bearings are going.

All those bits of metal are the reason why I now only use bearings with a polymer retainer instead of a steel or brass one. Bits of plastic won't cause nearly the same amount of damage if they break free. I think that all the 6902 bearings from rc-bearings.com have polymer retainers now and they're dirt-cheap too.

And you'd be well-advised to add a few oz of castor to that Coolpower fuel (or run Omega) so as to avoid rust in your other engines too. Besides which, *all* ABC/ABN engines will last much longer if they're run on fuel with a bit of castor in it.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I do not totally agree with the methods used in the video. It is not possible to heat a engine evenly with a gas flame or heat gun and this can cause the casing to warp. The best method for me is the kitchen stove. Pre-heat it to 180 C (356 F) and heat the casing for 10 minutes.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I tapped the connecting rod lightly with a hammer to flatten out any 'teeth' formed by the gouges. Going to run through the crankcase tomorrow with my Dremel and clean things up.

PB - the bearing set I bought was $7 so no worries to rebuild this one to get a few more flights out of it.

Lesson learned for next time regarding waiting to check things out.

One thing that confused me was the difference in condition between the front and rear bearing...

http://somegeek.home.comcast.net/som..._bearing_8.jpg

Curious why one looks so haggard and the other was like new. I will replace both bearings. Wonder if this was part of the batch of AX engines folks complained about with having cheap bearings?

XJet - I now add 4oz of Sig castor to each gallon of Cool Power 15% as added insurance. This engine had a few gallons of plain CP 15% before this.

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I had an OS 46fx once. Used lots of Castor and used after run oil everytime...........it still rusted[:@]

The rear bearing is directly in the Methanol and Nitromethane path, the front bearing does see oil but not as much methanol, Maybe it dries out easier.
and or is not near the combustion by products which are corrosive.

Good to hear about the added Castor in your cool power!

Richard

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I use an oven to heat the crankcase but if it needs just a little more heat, a torch works fine. There is no risk of warping a casting this small with the tiny amount of additional heat being added.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

My recent topic here about 46AX liner Peeling, involves the same thing that happened to your engine. After 2 - 1/2 gallons of CoolPower 10% the rear bearing went south but I caught it before any damage occured. Then with the new bearings and 3-4oz of castor added to future gallons, after another 2 - 1/2 gallons later, again rusted bearings with an extra: Liner peeled.. I changed all my fuels to omega after that.

CP is good as long as you get 20/20 pro pattern mix and above. other than that, Omega is the better choice.. thats my experience..

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Yep...the rear bearing has a much worse environment to live in than the front one.

Not to hijack the thread, but...I've been wondering for some time if the bearings that seem to rust so easily could be one of the reasons why some engines start to peel/flake?
The rust from the bearing is quite abrasive and could be a cause, or perhaps get the process started when it comes off the R. bearing and goes through the ports and up into the cylinder?

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I have agree the conrod is toast.[:o]

I also see a rather large gouge on the side of the piston in the last photo, although the pic is a bit blurry.

I've heard no mention of after run oil, in the arid climate up there, I would think it would be a must. I had the same problem with a 1.08, let the bearing go to long and let the conrod smash into the case for a flight or two.:eek:

Those are shards from the conrod not the bearing.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

There's mention in my original post... I mentioned that I didn't use it much. ;)

I was wondering if that was a possibility... how would the smooth conrod surface dig up the crankcase surface vs rub on it first? From looking at things, chunks of metal got lodged between the conrod end and the crankcase with lots of little bits of material breaking up and getting stuck in the piston and head.

The conrod moves freely on the crank end. Forgive my ignorance here... other than the surface being a bit gouged, what makes it toast?

somgeeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

That looks like one of the bad bearings that went out with some of the early motors. I could have sworn the two I replaced where Chinese made though, yours says Japan??

I've started replacing the 46 AX rear bearings with a Swiss made bearing from www.pspec.com even at $18 its insurance to me. I've tried the Ceramics from RC-Bearings and had 1 of 2 fail within a couple months of use. Perfomance Spec only sells the rear bearing, but the front seems to be ok for some reason.

Cool Power is definatley not helping you, adding Castor, or switching to Omega or Powermaster would be a better choice.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

daven - think 4oz of Sig castor per gallon of CP will help? I have another .46 AX that is older and running fine... think I will order a new rear bearing for it and cut it off at the pass. Are those $18 bearings less succeptable to rusting? Think I'll start using 1tsp of ATF until I get through my CP and start buying Omega.

Looking at the piston again, there are some scratches on the side from the debris but from looking at the chunks that passed up to the head, it could have been worse.

Either way - I'll rebuild this engine and run it. If it croaks it croaks.

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

somegeek,
You've most likely egged out the bronze bushing on the conrod. The reason I believe it's not from the bearing is all the shards are shiny aluminum.

How bad is the bottom of the case just below the conrod?

You might have had a piece in there from production that hit the bottom of the conrod, there's an awful lot of damage there.

In my case the bearings rusted and the play allows the conrod to start hitting the crankcase, I can't tell if initially that's what happened, but something large hit the rod.

Rust on bearings has to be really bad in your neck of the woods, I would be storing the plane inside the house rather than in the garage, if that's the case.
And of course run it dry after each flying session.
You really need to replace both bearings, I know the front looks fine, when the rear has that much play it pretty much destroys the front.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Close inspection of this joint shows zero play and I can't see any egging of the hole with the naked eye.
Just what you see in the pics. Few gouges from material lodged momentarily between the conrod and the crankcase.
There is zero damage or markings regarding the conrod rubbing against the crankcase.
This has been a concern(rust, warping balsa, etc) of mine since day one so my planes have been stored indoors though there are many a folk that store their planes in their garages with zero issues that I've read about.

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

If the crankcase is fine and you see no visible play in all directions on the conrod, you should be good to go with a bearing set. It can't hurt to try.

As Dar would say, get rid of that engine killing green fluid.:D:D

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Just a tip if you ever find yourself with an engine that has a lightly scored piston or bore.

Mix up a batch of fuel with 25%-30% castor oil.

Run the engine on that fuel and run it *very* lean for a couple of tanks.

Don't let it get so hot that it seizes -- keep the runs fairly short but hot.

You can then switch back to your regular fuel (so long as it also contains at least 2-3% castor).

I've done this a couple of times in the past and what happens is that the castor will form very hard varnish that fills the gouges on both the piston and the bore, promoting a better seal.

There are engines still running (good as new) in our club today after being "rescued" from piston/bore damage in this way.

It may not work every time but it's a *whole* lot cheaper than a new P/L set and there's really nothing to lose by trying it.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Adding 4oz of castor to the green stuff would help, but switching to Omega or Powermaster (my favorite) would be a better choice in my opinion. Morgan fuels does not recommend the green stuff (pure synthetic) in ABC / ABC / ABL type motors.

I prefer the swiss bearings as I believe they have tighter tolerances in their specs and the fact that we use this engine for local racing. The cheaper bearings normally work fine in a sport environment, but not always when you are taxing them at higher rpms.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Well I've had quite a few "original" bearings suffer from corrosion in TT, ST and Saito engines but the replacements I'm using from Paul have *never* shown any signs of corrosion.

I can't see the point in spending big-bucks on "name brand" bearings when Paul's do the job so very well and offer the extra benefit of dispensing with that dangerous metal retainer.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Is the upgrade for $5 to stainless races worth it or just go with the bearing steel races?

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

I don't thinkso -- generally it's not the races that corrode anyway -- it's the cages or the balls.

Stainless races are slightly softer than those from bearing steel so stainless bearings will wear a little more quickly (at least to start with) than plain bearings.

As I said -- I've never had one of Paul's standard bearings go rusty on me.

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Got my engine cleaned up. Lightly sanded the raised edges inside my crankcase...

http://somegeek.home.comcast.net/som...bearing_11.jpg

Removed the covers from both sides of the rear bearing and the back side of the front bearing and applied a healthy slathering of Sig Castor (this stuff is thick)...

http://somegeek.home.comcast.net/som...bearing_14.jpg

Lightly sanded the raised edges of the top of the piston and the head (wet sanded with 320 grit on a flat surface). Head was sanded by hand since the top is tapered. Just wanted to assure no raised edges would collide and cause more shards of metal.

http://somegeek.home.comcast.net/som...bearing_13.jpg

Took the time to break down the carb and then washed everything and used castor while I reassembled the engine.

The front bearing required some heat and then easily tapped into place. It inserted by hand about 1/4 of the way. Placed it on my work bench and patted the back of the crankcase down on it and it slid into place. I heated the crankcase next and the rear bearing almost dropped into place and then quickly cooled the crankcase which secured it. Reinstalled the rest of the parts and installed the engine back in my plane. It moves like new with all that castor in there and the new bearings. I hit it with a starter momentarily to see how it spun and it sounds good. Looking forward to firing it up tomorrow and also pondering xjet's method of forming a glaze to fill in the scratches in the piston and sleeve. Gonna see how things tach after a few tanks tomorrow.

Thanks for all the input guys. Will report back with my results.

somegeek

RE: O.S. .46 AX - bad rear bearing - metal shards... (pic heavy)
 

Geek,


I would not bother... This engine is utter junk!

Replacing all the parts to return the engine to 'a second before' status, will cost more than a new engine.


This, BTW, is the very reason to use only rear bearings with plastic material (phenolic, polyamide, Etc.) cages.

Just one 'shard' could do all this...